Areas of investigation included in this project are; 1) renal function in the presence of a reduced nephron population in man, with studies characterizing the functional pattern of the remaining kidney of transplant donors and that of residual nephrons in the chronically diseased kidney; 2) renal pharmacology in the dog utilizing micropuncture and chronic renal artery catheterization techniques, particularly to investigate the influence of vitamin D metabolites on phosphate transport, as well as the effects of vasopressin and corticosteroid administration; 3) renal pharmacology of lithium in man; 4) new techniques of kidney preservation and the development of techniques to assess the efficacy of preservation which will predict ultimate function following transplantation; 5) metabolic consequences of uremia, with an emphasis upon examining the effect of vitamin D metabolites and analogs in patients with chronic renal disease, synthesis of new vitamin D analogs and further elucidation of the events which control the synthesis of the active form of vitamin D by the kidney; and 6) studies of renal metabolism in health and disease, with emphasis upon studies of the characteristics of kidney mitochondria.